HRESULT 0xC05CFF01 (ERROR_SVHDX_UNIT_ATTENTION

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: The shared virtual disk reports a pending SCSI Unit Attention condition for this initiator.

Could be also:
Constant	Type	OS
STATUS_SVHDX_UNIT_ATTENTION_AVAILABLE	NTSTATUS	Windows

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ERROR_SVHDX_ERROR_NOT_AVAILABLE	ERROR_SVHDX_UNIT_ATTENTION_CAPACITY_DATA_CHANGED

ERROR_SVHDX_UNIT_ATTENTION_AVAILABLE

Meaning in the SCSI command path

ERROR_SVHDX_UNIT_ATTENTION_AVAILABLE tells the initiator that the virtual disk has Unit Attention information to report. Unit Attention is a SCSI changed-state condition: it is not the same as an ordinary permission error, media error, or a malformed command. It commonly appears after a state transition that requires the initiator to refresh what it knows about the device or shared-storage ownership.

The Shared VHDX layer can carry this condition across the remote virtual-disk path. A generic Unit Attention result does not identify the change by itself. The associated sense data determines whether the event concerns capacity, persistent reservations, registrations, an operating-definition change, or another unit-attention reason. This is why treating every instance as an automatic retry is unreliable.

How to handle the result

Collect the associated sense data and identify the precise Unit Attention reason before resuming a sequence of dependent I/O.
Re-read relevant device information and the current shared-disk state. For cluster-aware software, include persistent-registration and reservation status in that check.
Use the more specific Shared VHDX results when present. For example, preempted reservations, released reservations, and changed operating definitions require different recovery decisions.
Preserve the time order: a Unit Attention may be the first visible sign of a failover, registration change, device reconfiguration, or storage-format transition.

What not to conclude

This condition alone does not prove data corruption and does not say that a guest can safely reclaim shared-disk ownership. It says that an initiator must account for a state change. In a guest cluster, letting the cluster stack perform its normal fencing and ownership recovery is safer than issuing ad hoc SCSI Persistent Reserve Out commands from a troubleshooting host.

References

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